Shock absorber



Jan, 27, 1953 G, A, BRUNDRETT 2,626,685

SHOCK' BSORBER Jan. 27, 1953 G. A. BRUNDRl-:Tr 2,625,685

, sx-Iocx ABSORBER Filed oct. 14, 195o l 2 sHEETs-SHEET a Patented Jan. 27, 1953 UlllT'lE-IDvl STATES PATENT OFFIEE.

George A'.v v.Brl1nclrett; Dayton, v General Motors Gorporation, .corporationy of Delaware Ohio, assignon 'to Detroit, Micha. a`

Application October-14, 1950', SrialiNo'. 190,083"- 9'Glaims; 1.

This invention relates to an;` improved double acting-l hydraulic' Y'shock absorber: adaptedto-conf trol the approachingandlseparating movements of the frame and axle-of avehicle betweenwhich the shockabsorber1 connected'.

To -havel an hydraulic-shock absorber .operate atf-full' eiiiciency,- so that immediate and positive control is provided it is necessary that fluidi; sub.- stantially withouti air `contentlvbe provided inthe fluid@displacementchambers-fandlthati the cham@ ber ml'which pressure -is toibe'exertedf` upon.; its fluid content be completely filled.

` Itlisamong; the objectsv of? the lpresenti inven-s tion-tovprovide 'adouble acting hydraulic shock absorber inf which the fluid displacement cham.- ber, being-1lledWith-fluid'during then-stroke of the shock'- absorber 'inone' direction; hassaidfluid injected thereinto under pressure, whereby: the chamber is completely` lled and'- supercharged with a substantially airI free fluidi preparatory to having pressure exerted' thereuponr during` the next'strokeofthe shock absorber in thelopposite direction'.

This object is.aocompli'shed by'l forcing fluid', under pressurefromvalarger contracting chamberintoasmaIler expandingfchamber and'by providing a lluil discharge meansvloperative toe restrict the'transf'er ofthe eXcess-ludintol another chamber acting-as a receiving' chamber;

Further 4obiects and advantages offt'he present invention will'y be apparent fromthe. following description reference`lbeing hadto the-accompanyingrdrawings wherein aprefer-reciv embodiment of the presentimentionf is clearlyshown'.

In-the-,drawingsa Fig; 1 'is a longitudinalsectional fully-contracted shock absorber.

Fig:` 2 isa View "similar'to Eig'. lhshowing-f the shock absorber 'partiallyfexpand'edi Fig: 3 is-a. diagrammatic: viewi showing. the shock-f absorberapplied to au motor vehicle: between'- the rear axle: and. thelirame thereof: applied. to.. a motor vehicle. between tlief` rear: axle and' thefframefthere ofi Fig. fris; aztransverse sectional-view?. takenisub'r.- .stanti'ally along ithe line, and;V inthe-direction. of thefgarrowsd-diofig; 1.,

Figr is. aview :similar torFig; zbutta'ken-along the' line anuzxinV .the drection'zof .thearrovvs4 5 5 offEg..2'.

Fig. 6I is: a'. detail View.v of i'the .springimember of: onet'of `the vfluid owfcontrolvawes.

Fig. 7 is .ai side;l Viewv of: the' spring: shown'.` in Eig.; 6.

lili'f.V 8 isadetail view -fofx thefspring membersof another of thel fluidiffiow-=oontrolvalvesu.

viewf of 1"' the Referring: to the drawings andi' particularly: the Fig. 3 whichdiagrammatical-ly shows f the; 'shock absorberof the: present invention. appliedttoi Va motorvehicle, ,the numerall 20f-.designates the; axle ofthe vehicle: attached tofa yvehicle springrzlfthe ends; of which are. hingedly; secured tofth'e vehiclelframelfZ; 'The 'ax-le, -hasvthe wheeli2f3f of .the vehicle appliedthereto. 'Ehe-hydraulic `shock .absorber designate'dfasf a i whole thenumeral Z5 comprises: two. relativelyY movableportionsf or groups cf parts' onebeingA attached "to` the axle 20', theotlner to 'the-"frame:- 2,2.r of-the-rvehic1e-.

When ani obstruction Lin'- the roadway is'vmet-.by Y

thevehiclewheel 23 the axle 2li-is' thrustup- Wardiy'to approach the frame f22 therebpplacing thel spring; 2i' of: the vehicle under. compression. lThis approacl'iing` moi/ementof. -theaxle. 2f to- Ward the frame 22mm/es theassociatedparts ofl the-shock absorber 25 relativelyr to the asso.- ciated parts-of. the shock absorber connectedto the frame. 224 andvthusfthe shocleabsorber 251s contracted. For purposes offthisdescription the contractive-movement of. the shock absorber is referred to as its compression stroke fordur.- ing thistime ,the vehicle springv zlisplacedfunder compression.. The reaction tothiscompression of the spring 2.1.- is to causetthe frame 22am-be thrust upwardly thereby resulting, in. a.' separating movement oftheframefand axle-of,- the-ve.- hicle. This separating movement results `rinfan expanding;A of. the shock. absorber 25' due Stof-.the

relative v separating` movementsof .the portions `of the shock absorber attached to theaxle vandqtofthe frame. ofthe vvehicle respectively. In Tthis :movement of the. shock-y absorber itis referred ttofaswits rebound mov-ement resultingirom-the rebound-v ingl of theacompressed:vehiclefspring; 21 toward its normal VloadI position aterhaVing`- been moved on itsw compression4 stroke bp theestrikingr or. Van obstruction inztheroadway.

.'Itosimpliiv.j the. description and for purposes of facilitating4 a..clear understandingxthereof the partsV of ,theshoclr` absorberattached andmovable' directly with the axle 20 of theiveh-ic-letwillbe described. With; reference.V particularly tot the Figs. 1 and.v 2- the Y stub shaft `2 6a is .f-attachablevtothe axle-in anyfsuitable manner. .'Iofthisstub` shaft zthere` is #secured Yinanyfv suitabley Wayya cup.- shaped.' member. 251 which` forms amends closure cap for the outerftubularmember V28 of: the shock absorber..l The upper or opposite. end of;l this tubular. member! Sf'hasthe inverted Soup-shaped element 29g-attached thereto inzanysuitablemamner, the: cup:` 29# being" provided` with a1 central openingforfpurposeszt'ozfbe: described: The lower closure.: member: or cupv5 21 .has internal spaced ribs 3| upon which a valve cage 32 rests. This valve cage ts into and supports the one end of a tube 33 smaller in diameter than the outer tube 28 so as to provide an annular space between said two tubes which forms the uid reservoir 34. The upper or opposite end of the tube 33 has a closure member 35 tting into and upon it, this closure member being centrally apertured for purposes to be described and having an outwardly extending annular flange which fits into the portion of the upper closure member or cap 29, the body portion of the closure member extending telescopically into the outer tube 28. A plurality of notches 31 in the peripheral edge of the annular flange provides communication between the reservoir 34 and the space above said flange and inside the closure cup 29. A resilient package 38 is provided within the inverted closure cup 29 being urged into sealing engagement with the closure member and with the tube slidably supported in the central opening of closure member 35 which tubes extends through the central opening 3) in the closure member 29. The spring 40 lnterposed between the flange of the closure member 35 and an abutment washer on the resilient packing 38 exerts a constant force upon the packing to keep it in sealing engagement as mentioned.

The valve cage 32 resting and urged upon the ribs 3| in the closure member 21 partially telescopically fits into the tube 33 which forms the one working cylinder of the shock absorber. This valve cage has a plurality of through passages one group designated by the numeral 45 being arranged in a circular row, the other group 45 also being arranged in a circular row within the group 45. The valve cage 32 has a rod 41 centrally secured thereto in any suitable manner said rod being concentric with the working cylinder 33. An annular shoulder on rod 41 provides an abutment for the ring shaped body portion 48 of a spring, the resilient ngers 49 of which engage and yieldably urge the ring disc valve 50 upon the valve cage 32 to close the group of openings 45 in said valve cage. This valve 5i) will permit uid to flow from the chamber beneath the valve cage, which chamber is in communication with the reservoir 34, into the working cylinder 33, but will not permit fluid to flow from said cylinder into the reservoir. The openings 46 in the inner annular row are normally closed by a disc valve yieldably urged against the valve 'cage 32 by a star shaped spring 52, detailedly shown in Fig. S and supported upon an abutment washer 53 secured to the rod 41. Valve 5| is operative to permit fluid to ilow from cylinder 33 into the reservoir 34 under certain conditions but will not permit uid to flow in the opposite direction from the reservoir 34 into the cylinder 33. For purposes of this description the valve 50 will be referred to as the intake valve while valve 5| will be termed a fluid ow restricting valve.

The rod 41, carried by the valve cage 32 and extending coaxially into the cylinder 33, has a longitudinally central passage 55 extending from the inner end of the rod to a series of radial or cross-passages 56. The inner end of this rod 41 is screw threaded to receive the interiorly threaded end of a tubular piston 51. This piston 51 has an inner partition spaced from the end ofrod 41 when the piston is attached to said rod, this partition being provided with a central through passage in which the valve 58 issldiably carried. This valve 58 has a tubular shaped body portion provided with an enlarged solid head 59 which is yieldably maintained upon the inner Surface of the partition to close the passage therein by a coil spring 65 one end of which rests upon the upper surface of the partition in the piston the other end abutting upon a washer secured to the outer end of thetubular body portion of the valve. A slide slot 62 in the tubular body portion of the valve 58, is normally within the confines of the central passage in the partition of piston 51, said side slot however being eiective to provide communication between the interior of the tubular body portion of the valve 58 and the passage 55 in the rod 41, when pressure actaates the valve 58 against the effect of spring 6|) to move the head 53 of said valve out of engagement with the surface of the partition in piston 51. As shown in Figs. 1 and 2 the annular wall-of the piston 51 extends beyond the end of said valve 58. The elements aforedescribed are those which, assembled together, are secured to the axle 20 of the vehicle and move therewith.

Now the elements of the shock absorber assembled together and attached to and movable with the frame 22 of the vehicle will be described.

The rod 1a is attached to the frame of the vehiole 22 in any suitable manner. This rod 1G- has a plug 1| formed or secured thereon, said plug having a body portion provided with an annular groove 12 and is exteriorly threaded beneath said groove as at 13. The screw threaded end 13 of the plug 1| has the one end of a tube 14 threadedly secured thereto, the tube extending over and closing the annular groove 12 in the plug. To provide a seal at this point, this closed groove 12 contains any suitable resilient packing ring 15. The tube 14, threadedly attached to the block 1| as just described, extends through the central opening 30 in the upper closure cap 23 and is sealingly engaged by the packing 38 in said closure cap and is slidably supported with the central opening of the closure member 35. This tube extends coaxially into and through the tube 33 and being of smaller diameter than the inner diameter of the tube 33, forms the annular space 80, which may be termed the rebound compression chamber. This tube 14 has Va reduced outer diameter portion at its lower end upon which the second piston 8| of the shock absorber is mounted. The shoulder provided by the reduced diameter portion on tube 14 forms an abutment for the ring 82 which supports a valve controlling spring 83 detailedly shown in the Figs. 6 and 7. This spring has a solid annular ring portion fitting about the smaller diameter portion of tube 14 and abutting against the ring 32. The ring-shaped portion of this spring has resilient tongues S4 struck therefrom which are shaped to engage the ring shaped valve S5. and yieldably urge it upon the upper surface of the piston 8|. This piston has a plurality of passages 85, the upper ends of which are normally covered by the ring shaped valve 85,.the lower ends of which open into and communicate with the space'beneath the piston 8| and between said piston 3| and the valve cage assembly 32 at the bottom end of cylinder 33. The lower end of tube 14 is interiorly threaded to receivethe sleeve-shaped clamping nut 81 which presses and holds the piston 8| rigidly upon the rod 14 'so that any movement of the rod 14 up or down through its slidably supporting guide provided by the closure member35 will likewise move the piston 8| within the cylinder 33.

body of valve 96 out of the confines of the opening in the closure member 94 supporting the valve 96. This establishes a restricted fluid flow through valve 96 out of its side opening 91 into the now expanding chamber between the piston 51 and the closure member 94 of cylinder 9). The restriction to this fluid flow provided by valve 9S causes the shock absorber to offer a resistance to the separating movement of the axle 20 and the frame 22 of the vehicle. Inasmuch as the expanding chamber between piston 51 and the closure member Q4 is of lesser uid capacity than the rebound control chamber 80 and its associated space 9|, it cannot receive all of the fluid being forced from the said larger supercharged rebound control chambers 80, 93, 9|. The excess fluid transferred into the chamber above piston 51 under pressure, will be permitted to leak past the valve 58 which is opened for this purpose by the fluid pressure in the fluid compression chamber, this fluid leakage through valve 58 its side openings 62 into the chamber beneath the piston 51 and through passages 55 and 56 in the rod passing downwardly through the annular space between said rod 41 and the rod 9i) into the now expanding chamber beneath the piston 8|. Inasmuch as fluid is forced from the previously supercharged rebound control chamber into the compression control chamber during this movement of the shock absorber and the excess fluid flowing into the compression control chamber under pressure is permitted to leak restrictively therefrom past the valve which opens under these circumstances, this compression control chamber between piston 51 and the closure member 94 will be supercharged during this rebound stroke preparatory to the next reverse or compression stroke.

The fluid discharge from the compression control chamber past valve 58 during this movement of the shock absorber is insufficient to provide the proper fluid supply for the chamber beneath poston 8| and thus in response to the upward movement of piston 8| during this rebound stroke, valve 50 will be opened against the effect of spring lingers 49 to establish a replenishing flow of iiuid from the reservoir through passages 45 into the chamber beneath piston 8| and thus provide the proper fluid supply therefor.

From the aforegoing, it will be seen that the present shock absorber is completely supercharged, that is, each fluid displacement chamber does active work on one stroke at full efliciency and is supercharged during the other stroke. Fluid forced into the one chamber under pressure while the other chamber is active will lill said one chamber completely and with substantially air free fluid, thereby providing an incompressible medium in said chamber which immediately upon reverse movement of the shock absorber to render the supercharged chamber active, will provide full control, the complete filling of the chamber with substantially air free iiuid completely eliminating the lagging and spongy resulting effort provided by the shock absorber when a controlling chamber is only partially lled with fluid which contains an undesirable amount of compressible air.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A double acting hydraulic shock absorber of the direct acting type adapted to control the approaching and separating movements of two relatively movable members between which the shock absorber is connected, comprising in cornbination, a fluid reservoir; two cylinders each having a piston therein forming two fluid displacement chambers in each cylinder, the two chambers beneath the respective pistons being in constant communication, the two chambers above the respective pistons having a one-way valve interposed therebetween; a spring loaded valve in the one piston normally shutting off communication between the chambers on opposite sides of said one piston, said valve being operative at a predetermined fluid pressure in the chamber above said one piston to establish a restricted iiuid iiow through the piston into the chamber beneath said one piston, a second spring loaded valve in the second piston, normally shutting oli communication between the chambers above and beneath said second piston, said second valve being operative to establish a uid flow from the chamber beneath into the cham- 1 ber above said second piston, both piston valves being rendered active to establish their respective fluid flows in response to actuation of the shock absorber by the approaching movement of the two relatively movable members; iiuid iiow control means operative at a predetermined greater fluid pressure than necessary to open the valve in the said second piston, for establishing Y a fluid flow from the chamber beneath the both pistons into the reservoir; said one-way valve being operative at a predetermined pressure within the chamber above the second piston, resulting from the movement of said second piston by separating movement of the two relatively movable members, to establish a restricted iiuid flow from said chamber above the second piston into the chamber above the said one piston, the valve in said one piston being opened to establish a fluid leak from the chamber above said one piston caused by the differential fluid capacity of the two chambers above said pistons;

and a valve between the reservoir and chamber beneath the pistons, operative to establish fluid flow from the reservoir into the last mentioned chamber as the second piston is moved to increase the capacity ofthis chamber due to separation of the two relatively movable members.

2. A double acting hydraulic shock absorber of the direct acting type adapted to control the approaching and separating movements of two relatively movable members between which the shock absorber is connected, comprising in combination, a fluid reservoir; relatively movable cylinders and pistons providing a plurality of iiuid displacement chambers, above and below said pistons, the two chambers beneath the pistons being in constant communication and communicable with the iiuid reservoir; live fluid flow control valves in the shock absorber, the first being interposed between the chambers at opposite sides of the first piston, the second valve between the chambers at opposite sides of the second piston, both valves being concurrently operative by actuation of the shock absorber as the two relatively movable members approach each other, the iirst valve being operative to establish a shock absorber movement resisting fluid ow from the chamber above the first piston into the chamber beneath it, the second valve operative to establish a iiuid ow from the chamber beneath the second piston into the chamber above it, the third valve, interposed between thechambers beneath both .pistons and the reservoir being operative-at a fluid pressure higher .than -that `necessary to open the second valve, for establishing 4a fluid .flow into the reservoir as the-shock absorber -is actuated by the approaching movement of the two relatively movable members, vthe fourth valve, interposed between the two 4chambers above the two pistons, being-operative in response to fluid pressurein thev chamber above the second piston, as the/shock -absorber is actuatedbythe separation of the two relatively movable members, to establish a shock absorber-movement resisting from the chamber above the second piston into the chamberabove the iirst piston, afluid leak from said last mentioned Vchamber being established by the rst `Valvedue to the Asmaller fluid capacity of the chamber above the flrst piston, the fth valve provided between the chambers beneath -both pistons-and the reservoir being operative in response to the shock absorber actuation 'by theseparating movable members, to establish a ow from the reservoir into the two chambers beneath the pistons.

3. A double acting hydraulic shock absorber connected between the yframe and axle of a vehicle for controlling the-approaching and separating movement thereof, said shock absorber comprising, a fluid reservoir; two cylinders, one .withinthe other, each cylinder having a piston which forms an upper and a `lower fluid displacement chamber therein, the two -lower chambers of the respectivecylinders being in constant communication, the two upper chambers being in communication with each other onlythrough a pressure relief valve which is operative to establish a shock absorber movement resisting restricted flow of iiuid from the upper chamber of the larger cylinder into the upper chamber of the smaller cylinder as the-shock absorber is actuated by the separating movement of the frame and axle; and a uid ow restricting valve in the vpiston of the smaller cylinder, operative to perform two functions, the rst, to establish a restricted outlet for the excess fluid transferred from the larger into the .smaller upper chamber during said separating-movement of the frame and axle of the vehicle, whereby said smaller upper chamber is supercharged with iiuid preparatory to the reverse operation of the shock absorber, the second function of this valve being to establish a shock absorber movement resisting, restricted fluid ow from said supercharged smaller upper chamber as the shock absorber is actuated by the approaching frame and axle movement.

4. A shock absorber in accordance with claim 3, in which, however, a valve is interposed between the iiuid reservoir and the lower chambers beneath the two pistons, said valve being operative to establish a ow of fluid from the reservoir into said two lower chambers in response to the movement of the shock absorber by the separating action of the frame and axle of the vehicle.

5. A double acting hydraulic shock absorber connected between the frame and axle of a vehicle for controlling the approaching and separating movements thereof, said shock absorber comprising, a fluid reservoir; two cylinders, one within the other, each cylinder having a piston which forms an upper and a lower fluid displacement chamber therein, the two lower chambers of the respective cylinders being in constant communication; a valve in the piston within the inner and smaller diameter cylinder said valve being operative as the shock absorber is actuated by the flow frame and .axle of Ythe 'vehicle as they approach each other, to establish a shock absorber movement resisting, restricted fluid flow from the chamber above said smaller piston into thev chamber therebeneath and its communicating chamber beneath the larger piston; a valve in l'the larger piston operative at a predetermined fluid pressure'in the chamber beneath the larger'piston to establish a flow of fluid from saidchamber beneath into the chamber above said-larger piston; and a valve interposed between the said chamber .beneaththe 'piston and the reservoir, this .valve being operative at a higher pressure than that which opensthe valve in the larger piston for establishing the transfer of fluid from the chamber beneath the piston into the reservoir whereby the chamber above `the larger piston is supercharged and fluid. not receivable by the las't mentioned chamber is transferred to the reser- Voir during the actuation of the shock absorber by the frame and axle moving to approachea'clh other.

6. A double acting hydraulic shock absorber connected between two relatively movable'members for controlling their approachingand separating movements, the portion of the shock 'absorber connectible to one of said members comprising, two tubes of different diameters, one within the other and held concentric by a vclosure'at each end of the tubes, the outer tube cooperating with the inner tube, which forms one working cylinder, to provide a iluid reservoir, avalve cage in the cylinder end adjacent the4 movable member to which said cylinderlis attached, said .valve 'ca'ge having a plurality of passages certain of which are normally closed by va pressure relief valve operative only to permit fluid toiiow from-'the cylinder into the reservoir, the others being normally 'closed by 'an intake valve operative only to permit fluid to flow from Ythe reservoir into Athe cylinder, said valve supporting a rodextending centrally into .the cylinder said rod-providing one piston of the shockabsorber, said piston having a passage normally closed by a spring loaded valve operative Ato establish aiiuid flow throughthepiston and rod only in the direction toward the-valve cage, the other portion of the shockabsorber connectible to the other of said relatively movable members comprising a tube slidably supported by tbe closure of the aforementioned cylinder which 1s larger in diameter than said tube, a piston, the second of the shock absorber, secured to said tube and slidable in said cylinder. said second piston being provided with a valve operative only to permit uid to flow from the chamber between said second piston and the valve cage into the cylinder chamber on the opposite side of said second piston, a tube smaller in diameter than and supported within the tube carrying the second piston, this smaller tube forming the second cylinder in which the said one piston reciprocates the space between the second cylinder and its surrounding tube being in constant communication with the space between said tube and the said one working cylinder, the end of said second cylinder opposite that supported by the second piston having a closure member provided with a valve operative to establish a restricted iluid ilow from the said one working cylinder into the second cylinder.

7. A double acting hydraulic shock absorber connected between the frame and axle of a vehicle for controlling the approaching and separating movements thereof, said shock absorber comprismg a fluid reservoir, two working cylinders one larger 1n diameter than the other, each having 1 1 a piston forming fluid displacement chambers therein, a uid flow control valve in each piston, the valve in the one piston restricting uid flow through said one piston in one direction as said one piston moves in either direction and the valve in the second piston permitting the transfer of iluid from one side thereof to the other in response to movement of said second piston in one direction only, and a spring loaded valve between the cylinder containing the second piston and the reservoir providing for the restricted transfer of fluid from said last mentioned cylinder into the reservoir in response to actuation of the shock absorber by the frame and axle when approaching each other, said restricted transfer of uid causing the shock absorber to resist this frame and axle movement and the iiuid receiving chamber on the one side of the second piston to be supercharged with fluid preparatory to the reverse shock absorber movement.

8. A shock absorber in accordance with claim 7 in which, however, the displacement chamber on the one side of the said one piston is in fluid receiving communication with the iiuid discharging, supercharged chamber on the one side of the second piston through a fluid flow restricting control valve as the shock absorber is actuated by the frame and axle of the vehicle moving to separate, this restricted iluid flow causing the shock absorber to resist such frame and axle movements, the valve in the said one piston being operative to provide a uid leak for the excess uid entering the smaller diameter receiving chamber from the larger diameter supercharged chamber, whereby the smaller chamber is supercharged, and a iiuid intake valve interposed between the reservoir and cylinders, operative to establish a replenishing fluid ow from the reservoir into the cylinders in response to this actuation of the shock absorber.

9. A double acting hydraulic shock absorber of the direct acting type in which relatively movable portions are telescopically actuated toward each other on the compression stroke and away from each other on the rebound stroke of the shock 45 absorber which comprises in combination a fluid reservoir; two cylinders; a piston in each cylinder dividing it into two Working chambers, the

12 two chambers beneath the respective pistons being in communication with each other and the two chambers above the respective piston also being in communication with each other; a two way valve mechanism interposed between the lower cylinder chambers and the reservoir said mechanism consisting of an intake valve operative to permit uid to iiow from the reservoir into said lower chambers in response to movement of the one piston away from said mechanism and a pressure relief valve operative to permit iluid ow from said lower chambers into the reservoir in response to movement of said one piston on its movement toward said valve mechanism; a valve in said one piston operative to permit flow of uid from the chamber beneath the piston into the chamber above it as this piston moves on its stroke toward said valve mechanism said piston valve opening at a predeterminately lower pressure than the pressure relief valve in the valve mechanism; a spring loaded relief valve interposed between the two chambers above the respective pistons said valve being operative to permit a restricted iiuid iiow from the chamber above the aforesaid valved piston into the chamber above the other piston, the latter chamber being of predeterminately lesser capacity than the chamber above the valve piston; and a spring compression relief loaded valve, in said other piston operative to establish a restricted fluid flow from the chamber above it into the lower chamber as the shock absorber is actuated on its compression stroke, said compression relief valve being operative also to establish a iiow from the chamber above the piston carrying said valve, during the rebound stroke of the shock absorber.

GEORGE A. BRUNDRETT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name DateV 2,500,708 Rossman Mar. 14, 1950 2,519,605 Rossman Aug. 23, 1950 

